Building block



FIG. 1 is a front perspective view of a building block.

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The solid line showing illustrates the claimed features within the design for the claimed article of manufacture. The broken lines depict portions of the building block that form no part of the claimed design. The shading is provided to illustrate contour only and is not an indication of texture, gloss, etc. 

CLAIM The ornamental design for a building block, as shown and described. 